Fats/Oils - Shortening, Aeration, Plasticity and Emulsification

Fats and Oils in Food

Shortening refers to the ability of fats and oils to give a short, crumbly texture to baked goods.
The term comes from the notion of ‘shortening’ the dough’s strands of gluten, which gives the final product a tender quality.
Fats interfere with the gluten formation by coating the flour proteins and preventing them from absorbing water and forming long gluten strands.
Shortening is particularly noticeable when making pastry or scones, where fat is ‘rubbed into’ the flour.

Aeration is the process of incorporating air into a mixture to make it light and fluffy.
In baking, this is often achieved by creaming fat and sugar together. The sugar crystals cut into the fat, creating tiny pockets of air.
Aerated fat contributes to the light texture of cakes and biscuits.
The trapped air expands upon heating, helping the baked goods to rise and giving them a light, fluffy texture.

Plasticity refers to the ability of fats to change shape but not volume under pressure, a key property for many cooking and baking processes.
Not all fats have the same degree of plasticity. Butter, for instance, is more plastic than margarine because it can be spread thinly without breaking apart, providing consistent coverage.
Plasticity of fats allows for easy manipulation in baking. A plastic fat can be spread, rolled, or creamed more effectively.
Factors affecting the plasticity of fats include temperature and fat type. Too cold, and fats become brittle; too warm, and they become oily.

Emulsification is a process that combines two immiscible liquids, such as oil and water, often with the help of an emulsifier.
Emulsifiers are substances that sit on the boundary between oil and water, reducing the surface tension and allowing them to mix. In food, common emulsifiers are egg yolks, mustard and honey.
An example of emulsification in cooking is the making of mayonnaise or salad dressing, where oil is added to a vinegar or lemon juice base and the two are combined into a homogeneous mixture.
Emulsification helps in achieving desirable textures in sauces, dressings, and some baked goods. The even dispersion of oil and vinegar in a salad dressing, for instance, helps it coat the salad leaves more effectively.

Understanding these properties of fats and oils helps in creating desired textures and flavours in cooking and baking.
The shortening effect of fat gives pastries and biscuits their crumbly texture.
Aeration, achieved through the creaming of fat and sugar, contributes to the lightness and fluffiness of cakes.
The plasticity of fats allows for easier manipulation in baking, impacting the final texture and mouthfeel of the food.
Emulsification helps in creating stable mixtures of oil and water, contributing to the creaminess of sauces and dressings.